<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0,user-scalable=no">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>计算属性</title>
    <script src="https://cdn.bootcss.com/vue/2.5.21/vue.js"></script>
</head>

<body>
    <div id="app">
        {{sum}}
    </div>
    <script>
        new Vue({
            el: "#app",
            data: {
                sum1: 1,
                sum2: 2,
                sum:3
            },
            watch: {
                num1(){
                    this.sum = this.num1+this.num2;
                },
                num2(){
                    this.sum = this.num1+this.num2
                }
            }

            // computed: {
            //     sum(){
            //         return this.num1+this.num2
            //     }
            // }
        })

    </script>
</body>

</html>